Three-Dimensional Anisotropic Microlaser from GaN-Based Self-Bent-Up Microdisk

Microcavities with whispering gallery modes (WGM), usually formed by two-dimensional (2D) circular structures, are significant elements in integrated optics, quantum information, and topological photonics. We report three-dimensional (3D) WGM from self-bent-up microdisks consisting of strain-released AlGaN/GaN bilayers, which provide an extra degree of freedom of the WGM photons in the vertical dimension, in contrast with the 2D WGM whose field mainly distributes in the horizontal plane. Despite the ultrathin and deformed cavity layer, the 3D WGM shows a reasonably high quality factor for GaN-based microdisks (similar to 1300) and exhibits single mode lasing due to the anisotropic feature of the bent-up disk, a unique advantage over the conventional planar microdisks of the same material and size. Such devices provide altitude dependence of emitting direction and are promising for applications in multilevel integrated photonics circuits.